This invention relates generally to inflators for use in inflating inflatable restraint airbag cushions, such as used to provide impact protection to occupants of motor vehicles. More particularly, the invention relates to inflator devices having multiple or plural stages or levels of inflation gas output and as such may be used to provide an inflation gas output which is adaptive to factors such as one or more crash and occupant conditions.
It is well known to protect a vehicle occupant using a cushion or bag, e.g., an “airbag,” that is inflated or expanded with gas when the vehicle encounters sudden deceleration, such as in the event of a collision. In such systems, the airbag cushion is normally housed in an uninflated and folded condition to minimize space requirements. Upon actuation of the system, the cushion begins being inflated in a matter of no more than a few milliseconds with gas produced or supplied by a device commonly referred to as an “inflator.”
Various types of inflator devices have been disclosed in the art for the inflation of an airbag such as used in inflatable restraint systems. One type of known inflator device derives inflation gas from a combustible pyrotechnic gas generating material which, upon ignition, generates a quantity of gas sufficient to inflate the airbag.
In view of possibly varying operating conditions and, in turn, possibly varying desired performance characteristics, there is a need and a desire to provide what has been termed an “adaptive” inflator device and a corresponding inflatable restraint system. With an adaptive inflator device, output parameters such as one or more of the quantity, supply, and rate of supply of inflation gas, for example, can be selectively and appropriately varied dependent on selected operating conditions such as one or more of ambient temperature, occupant presence, seat belt usage and rate of deceleration of the motor vehicle, for example.
Pyrotechnic inflator typically may have one or more chambers containing gas generant. Adaptive pyrotechnic inflators having gas generant material in two chambers, which are independently ignited by two igniters have been referred to as “dual stage” inflators. In practice, each such gas generant material-containing chamber is oftentimes referred to as a “combustion chamber” as the gas generant material therein contained is burned or otherwise reacted to produce or form gas such as may be used to inflate an associated inflatable restraint airbag cushion.
Dual stage inflators may have several contemplated firing scenarios. In a first such scenario, only the gas generant material in a first or primary chamber is actuated whereby a fixed quantity of inflation gas is produced thereby. In a second possible firing scenario, the first or primary chamber is first actuated whereby gas generant material in the first chamber is first reacted to start to produce or form inflation gas and after a predetermined or preselected delay, the gas generant material in a second or secondary chamber is then actuated whereby gas generant material in the second chamber is reacted to also produce or form inflation gas. In a third possible firing scenario, the gas generant material in the first chamber and the gas generant material in the second chamber are actuated simultaneously to produce or form inflation gas from the gas generant material in each of the chambers.
As will be appreciated, through the selection and use of an appropriate such firing scenario, inflator output parameters such as one or more of the quantity, supply, and rate of supply of inflation gas, for example, can be selectively and appropriately varied dependent on selected operating conditions such as one or more of ambient temperature, occupant presence, seat belt usage and rate of deceleration of the motor vehicle, for example.
Particular known adaptive inflator devices include commonly assigned U.S. Pat. No. 6,032,939, issued 7 Mar. 2000 to Mossi et al., and U.S. Pat. No. 6,189,927, issued 20 Feb. 2001 to Mossi et al., which teach such inflator devices that include two discrete and isolated chambers of gas generant materials and permit several distinct inflation performance scenarios while desirably employing a single set of inflation gas treatment components such as filters for the treatment of products of both chambers.
U.S. Pat. No. 7,044,502, issued 16 May 2006, discloses a dual stage inflator having a movable divider plate that separates gas generant material in a primary chamber from gas generant material in a secondary chamber. The patent discloses that before the inflator is fired, the divider plate rests against the inner surface of the lower housing. The divider plate thus prevents inflation gas from the primary chamber from igniting the secondary chamber. However, when the internal pressure of the secondary chamber exceeds the internal pressure of the primary chamber, the divider plate is displaced in an upward direction thereby permitting the inflation gas from the secondary chamber to flow around the divider plate and out of the inflator.
Reliance on movement of a chamber divider plate can lead to an inflator device experiencing undesired performance variability and may also lead to less efficient than desired control of the combustion pressure in one or both of the inflator device combustion chambers.
Adaptive inflator devices find widespread use in modern day vehicle occupant safety restraint systems. Such use leads to a need and desire for improved adaptive inflator devices such as capable of specifically varying selected inflation performance scenarios. Thus, there is a need and demand for adaptive inflator devices and associated methods of operation of increased simplicity and reliability of operation and design. In particular, there is a need and demand for adaptive inflator devices and associated methods of operation that provide or result in specifically desired inflation performance scenarios in a less costly and/or more efficient manner.